The use of a clumping type of litter in animal litter boxes, such as, for example, cat litter boxes, has desirable features. The clumping of the litter upon contact by liquid waste material such as urine allows the waste material to be easily separated from the uncontaminated litter. Commonly, the clumps of litter and the fecal material in the litter box after use by an animal are removed by scooping the litter with a slotted or perforated spoon to sift the unclumped litter from the waste material. In this manner, the uncontaminated litter can be, at least in theory, kept clean for continued use by the animal. Litter removed with the waste material is generally periodically replaced to maintain a sufficient quantity of litter in the box for use by the animal.
Sifting the litter with the scooping spoon is undesirable. The chore can be time-consuming and often not as effective as desired. For example, if the slots in the spoon are too large, smaller pieces of soiled litter and waste material cannot be separated. Or, if the sifting action is too vigorous, the clumps of litter can be disturbed and broken so that they are not removed from the litter.
Various forms of quick sifters for litter boxes using clumping litter have been proposed. One type of quick sifter in the prior art is made of rigid materials, as in U.S. Pat. No. 4,217,857 to Geddie. Not originally designed for use with clumping litter, this rigid box quick sifter uses a rigid screen pan and two receiving pans that nest or stack together. The litter is cleaned by lifting out the screen pan to sift the litter from the fecal material, placing the screen pan in the unused receiving pan, and pouring in the screened litter to cover the screen. The emptied pan is then nested under the filled receiving pan until the next litter cleaning. However, when the rigid box quick sifter is used with clumping litter, the clumps adhere to the sides and bottom of the screen pan, and in some cases form directly in the grid of the screen. These clumps stuck on or in the screen pan complicate the sifting operation and necessitate cleaning of the screen pan.
Another rigid box quick sifter uses three nested pans with longitudinal spaced-apart slats in the bottom of each pan which are offset from each other by rotating 180 degrees, as in U.S. Pat. No. 5,325,815. These quick sifters have the same problems noted with the Geddie device, but also suffer from urine leakage through the spaces between the slats if the pans are aligned improperly, as when one inadvertently forgets to rotate the bottom pans, or if litter accumulates between the pans and prevents the pans from nesting properly.
Disposable liners having holes formed therethrough in a spaced-apart manner have also been proposed, as in U.S. Pat. No. 5,121,712. These liners still have a number of drawbacks. For example, the holes are usually sized and spaced in a manner which does not allow the unsoiled litter to flow rapidly or completely freely from the sifting liner, with the result that these sifters are not quick enough for the convenience of some consumers. The relatively large perforations through the liner can allow smaller pieces of soiled litter to pass through the liner and contaminate the relatively clean litter. Moreover, these types of sifters are disposable and designed for a single use. Usually made of plastic film, these sifters are not durable.
There remains a need in the art for a reusable quick sifter for use with clumping litter which is economical for everyday use, inhibits passage of urine from the litter box, keeps the side walls of the box clean, is easy to clean and keep aligned for sifting, and quickly and easily effects the sifting operation.